Question

2) Describe the antero-posterior patterning of the dorsal wing imaginal disc, including the major genes involved and their role in this patterning. 3) Describe the antero-posterior, dorso-ventral and proximo-distal patterning of the ventral leg imaginal disc, including the major genes involved and their role in patterning.

Answer 1

2)· In the stage before fertilization, the anterior posterior axis of the future embryo becomes defined by 3 system of molecule that create Landmark in the oocyte.

· Following fertilization each Landmark serves as a beacon, providing a signal, in the form of morphogen gradient that organises the development process in its neighbourhood.

· Two of these signals are generated from localised deposits of specific in mRNA molecules.

· The future anterior in of the embryo contains high concentration of mRNA for a gene regulatory protein called Bicoid.

· This mRNA is translated to produce Bicoid protein ,which diffuses away from its source to form a concentration gradient with its maximum at the anterior end of the egg .

· The future posterior end of the embryo contains high concentration of mRNA for the regulator of translation called Nanos, which sets up posterior gradient in the same way .

· The third signal is generated symmetrically at the both ends of the egg, by local activation of a transmembrane tyrosine kinase receptor called Torso.

· The activated receptor exert its effect over a short arrange makes the sites of specialised terminal structure that will form at the head and a tail end of the future Lava and also defining the rudiments of future gut.

· The three sets of the genes responsible for the localised determines are referred to as anterior posterior and terminal set of egg polarity gene .